The present invention relates to a unit cuvette capable of containing a biological fluid, in order to analyze said fluid, and to an automatic analyzer comprising such cuvettes for in vitro analysis.
Document EP 0 325 874 teaches a cuvette for determining the clotting time of blood. For this purpose, the bottom of the cuvette comprises a curved raceway with an upwardly directed concavity, on which a ferromagnetic ball is placed and driven in a periodic movement under the effect of an external magnetic field. By detecting the variations in amplitude and/or frequency of the movement of the ball it is possible to measure the clotting time. This measurement is carried out by means of a densitometer placed in such a way that the light beam that it produces is approximately tangential to the ball when it is at the lowermost point of the raceway. The cuvettes may be used either individually or in blocks of several cuvettes.
This type of cuvette, although generally satisfactory, nevertheless has a number of drawbacks.
Firstly, when the cuvettes disclosed in document EP 0 325 874 are used individually, it is difficult or time-consuming to store them in an ordered manner, which saves space, without it being tricky to separate the cuvettes from one another by means of a controller. Conversely, when several cuvettes are formed as a single block, storage is easier, even if a greater volume may be required. However, handling such a block may prove awkward in certain applications and, in any case, it is difficult if not impossible to carry out different tests on the cuvettes of a given block, unless a very specific analyzer is provided.
Furthermore, these cuvettes are solely intended for determining the clotting time of blood and, for this purpose, they all have a ball. Of course, it is possible to use these cuvettes for performing other analyses or measurements on the biological fluid that they contain, but this involves the following drawbacks:                the cost of a cuvette is needlessly increased because of the unnecessary presence of a ball on the one hand, and means provided on the cuvette for preventing the ball from escaping on the other;        the presence of a ball may prove problematic in the case of certain tests (especially immunology tests using magnetic particles); and        in the case of photometric measurements, it is necessary to increase the reaction volume so as to cover the ball with a sufficient height so as to carry out the optical measurement escaping the ball. The cost of the test is therefore increased owing to unnecessary amounts of reactants.        
The present invention aims to remedy the abovementioned drawbacks.